diff --git a/common/bspfile.cc b/common/bspfile.cc
index a4c3f746..2791137a 100644
--- a/common/bspfile.cc
+++ b/common/bspfile.cc
@@ -358,6 +358,28 @@ public:
         }
     }
 
+    contentflags_t visible_contents(const contentflags_t &a, const contentflags_t &b) const override
+    {
+        if (a.equals(this, b)) {
+            return create_empty_contents();
+        }
+
+        int32_t a_pri = contents_priority(a);
+        int32_t b_pri = contents_priority(b);
+
+        if (a_pri > b_pri) {
+            return a;
+        } else {
+            return b;
+        }
+        // fixme-brushbsp: support detail-illusionary intersecting liquids
+    }
+
+    bool contents_contains(const contentflags_t &a, const contentflags_t &b) const override
+    {
+        return a.equals(this, b);
+    }
+
     std::string get_contents_display(const contentflags_t &contents) const override
     {
         std::string base;
@@ -850,6 +872,9 @@ struct gamedef_q2_t : public gamedef_t
         return true;
     }
 
+    /**
+     * Returns the single content bit of the strongest visible content present
+     */
     constexpr int32_t visible_contents(const int32_t &contents) const
     {
         for (int32_t i = 1; i <= Q2_LAST_VISIBLE_CONTENTS; i <<= 1) {
@@ -907,6 +932,18 @@ struct gamedef_q2_t : public gamedef_t
         return {a.native | b.native};
     }
 
+    contentflags_t visible_contents(const contentflags_t &a, const contentflags_t &b) const override
+    {
+        int viscontents = visible_contents(a.native ^ b.native);
+
+        return {viscontents};
+    }
+
+    bool contents_contains(const contentflags_t &a, const contentflags_t &b) const override
+    {
+        return (a.native & b.native) != 0;
+    }
+
     std::string get_contents_display(const contentflags_t &contents) const override
     {
         if (!contents.native) {
diff --git a/include/common/bspfile.hh b/include/common/bspfile.hh
index 76b659de..b9b138cb 100644
--- a/include/common/bspfile.hh
+++ b/include/common/bspfile.hh
@@ -292,6 +292,8 @@ struct gamedef_t
     virtual bool contents_seals_map(const contentflags_t &contents) const = 0;
     virtual contentflags_t contents_remap_for_export(const contentflags_t &contents) const = 0;
     virtual contentflags_t combine_contents(const contentflags_t &a, const contentflags_t &b) const = 0;
+    virtual contentflags_t visible_contents(const contentflags_t &a, const contentflags_t &b) const = 0;
+    virtual bool contents_contains(const contentflags_t &a, const contentflags_t &b) const = 0;
     virtual std::string get_contents_display(const contentflags_t &contents) const = 0;
     virtual void contents_make_valid(contentflags_t &contents) const = 0;
     virtual const std::initializer_list<aabb3d> &get_hull_sizes() const = 0;
diff --git a/include/qbsp/portals.hh b/include/qbsp/portals.hh
index 538ec68a..a48c5a1a 100644
--- a/include/qbsp/portals.hh
+++ b/include/qbsp/portals.hh
@@ -34,6 +34,7 @@ struct portal_t
     portal_t *next[2]; // [0] = next portal in nodes[0]'s list of portals
     std::optional<winding_t> winding;
 
+    bool sidefound; // false if ->side hasn't been checked
     face_t *side; // NULL = non-visible // fixme-brushbsp: change to side_t
     face_t *face[2]; // output face in bsp file
 };
@@ -56,3 +57,4 @@ void MakeTreePortals(tree_t *tree);
 void FreeTreePortals_r(node_t *node);
 void AssertNoPortals(node_t *node);
 void MakeHeadnodePortals(tree_t *tree);
+void MarkVisibleSides(tree_t *tree, mapentity_t* entity);
diff --git a/qbsp/portals.cc b/qbsp/portals.cc
index 83b0167e..d08c0ff5 100644
--- a/qbsp/portals.cc
+++ b/qbsp/portals.cc
@@ -426,3 +426,119 @@ void FreeTreePortals_r(node_t *node)
     }
     node->portals = nullptr;
 }
+
+//==============================================================
+
+/*
+============
+FindPortalSide
+
+Finds a brush side to use for texturing the given portal
+============
+*/
+static void FindPortalSide(portal_t *p)
+{
+    // decide which content change is strongest
+    // solid > lava > water, etc
+    contentflags_t viscontents = options.target_game->visible_contents(p->nodes[0]->contents, p->nodes[1]->contents);
+    if (viscontents.is_empty(options.target_game))
+        return;
+
+    int planenum = p->onnode->planenum;
+    face_t *bestside = nullptr;
+    float bestdot = 0;
+
+    for (int j = 0; j < 2; j++)
+    {
+        node_t *n = p->nodes[j];
+        auto p1 = map.planes.at(p->onnode->planenum);
+
+        for (brush_t *brush : n->original_brushes)
+        {
+            if (!options.target_game->contents_contains(brush->contents, viscontents))
+                continue;
+            for (face_t &side : brush->faces)
+            {
+                // fixme-brushbsp: port these
+//                if (side.bevel)
+//                    continue;
+//                if (side.texinfo == TEXINFO_NODE)
+//                    continue;		// non-visible
+                if (side.planenum == planenum)
+                {	// exact match
+                    bestside = &side;
+                    goto gotit;
+                }
+                // see how close the match is
+                auto p2 = map.planes.at(side.planenum);
+                float dot = qv::dot(p1.normal, p2.normal);
+                if (dot > bestdot)
+                {
+                    bestdot = dot;
+                    bestside = &side;
+                }
+            }
+        }
+    }
+
+gotit:
+    if (!bestside)
+        logging::print("WARNING: side not found for portal\n");
+
+    p->sidefound = true;
+    p->side = bestside;
+}
+
+/*
+===============
+MarkVisibleSides_r
+
+===============
+*/
+static void MarkVisibleSides_r(node_t *node)
+{
+    if (node->planenum != PLANENUM_LEAF)
+    {
+        MarkVisibleSides_r(node->children[0]);
+        MarkVisibleSides_r(node->children[1]);
+        return;
+    }
+
+    // empty leafs are never boundary leafs
+    if (node->contents.is_empty(options.target_game))
+        return;
+
+    // see if there is a visible face
+    int s;
+    for (portal_t *p=node->portals ; p ; p = p->next[!s])
+    {
+        s = (p->nodes[0] == node);
+        if (!p->onnode)
+            continue;		// edge of world
+        if (!p->sidefound)
+            FindPortalSide(p);
+        if (p->side)
+            p->side->visible = true;
+    }
+}
+
+/*
+=============
+MarkVisibleSides
+
+=============
+*/
+void MarkVisibleSides(tree_t *tree, mapentity_t* entity)
+{
+    logging::print("--- {} ---\n", __func__);
+
+    // clear all the visible flags
+    for (auto &brush : entity->brushes) {
+        for (auto &face : brush->faces) {
+            face.visible = false;
+        }
+    }
+
+    // set visible flags on the sides that are used by portals
+    MarkVisibleSides_r (tree->headnode);
+}
diff --git a/qbsp/qbsp.cc b/qbsp/qbsp.cc
index 41b75d30..fb044970 100644
--- a/qbsp/qbsp.cc
+++ b/qbsp/qbsp.cc
@@ -902,7 +902,8 @@ static void ProcessEntity(mapentity_t *entity, const int hullnum)
 
         MakeTreePortals(tree);
 
-        MakeVisibleFaces(entity, tree->headnode);
+        MarkVisibleSides(tree, entity);
+        MakeFaces(tree->headnode);
 
         if (hullnum <= 0 && entity == map.world_entity() && !map.leakfile) {
             WritePortalFile(tree);
diff --git a/qbsp/surfaces.cc b/qbsp/surfaces.cc
index f7515758..fd67e593 100644
--- a/qbsp/surfaces.cc
+++ b/qbsp/surfaces.cc
@@ -750,10 +750,12 @@ static face_t *FaceFromPortal(portal_t *p, int pside)
     f->planenum = side->planenum;
     f->planeside = static_cast<side_t>(pside);
     f->portal = p;
+    f->lmshift = side->lmshift;
 
     // don't show insides of windows
-    if (!side->contents[1].is_mirrored(options.target_game))
-        return nullptr;
+    // fixme-brushbsp: restore this?
+//    if (!side->contents[1].is_mirrored(options.target_game))
+//        return nullptr;
 
     if (pside)
     {
@@ -766,6 +768,9 @@ static face_t *FaceFromPortal(portal_t *p, int pside)
         f->w = *p->winding;
         f->contents[1] = p->nodes[0]->contents;
     }
+
+    UpdateFaceSphere(f);
+
     return f;
 }
 
@@ -812,7 +817,7 @@ static void MakeFaces_r(node_t *node, makefaces_stats_t& stats)
         face_t *f = FaceFromPortal(p, s);
         if (f)
         {
-            c_nodefaces++;
+            stats.c_nodefaces++;
             p->face[s] = f;
             p->onnode->facelist.push_back(f);
         }